01 -
Heat a large sauté pan over medium-high heat. Add butter or margarine, then cook ground beef and diced onions together, breaking up the meat until browned and onions are soft, about 6 to 8 minutes. Drain excess grease.
02 -
Add 2 cups of water to the pan. Stir in broken spaghetti and distribute evenly. Cover and cook over medium-high heat for 4 minutes until pasta begins to soften.
03 -
Uncover and stir in marinara sauce, salt, pepper, onion powder, and garlic powder. Mix thoroughly and reduce heat to low. Simmer until pasta is fully cooked and sauce thickens slightly.
04 -
While pasta finishes cooking, place split buns cut-side up on a baking sheet. Spread with garlic butter and toast in a 400°F oven for 4 to 6 minutes until golden.
05 -
Remove pan from heat and stir shredded mozzarella into the hot pasta mixture. Mix until cheese is melted and the filling is creamy and cohesive.
06 -
Spoon generous portions of cheesy spaghetti filling onto the toasted bun bottoms. Top with the remaining bun halves and serve immediately while hot.